Aluminum nitride sintered body and electrostatic chuck

Abstract

To provide an aluminum nitride sintered body exhibiting excellent insulation in a high temperature region, and an electrostatic chuck.SOLUTION: The aluminum nitride sintered body is mainly composed of aluminum nitride (AlN), and includes a composite oxide (R-Al composite oxide) containing a rare earth element and aluminum, and magnesium oxide (MgO), wherein the R-Al composite oxide and the magnesium oxide are present between particles of the aluminum nitride, and the volume resistivity thereof at 600°C is 1.0×109 Ωcm or more and 1.0×1012 Ωcm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an aluminum nitride sintered body and an electrostatic chuck. [Background technology]

[0002] Conventionally, ceramic components have been used in semiconductor manufacturing equipment as electrostatic chucks, heaters, etc. In recent years, semiconductor manufacturing has come to be carried out at high temperatures of 600°C or higher in order to achieve miniaturization and higher density of semiconductor integrated circuits, and there is a demand for ceramic components with excellent insulation properties at high temperatures.

[0003] For example, Patent Document 1 listed below discloses an aluminum nitride sintered body that includes aluminum nitride (AlN) crystal particles containing Mg (magnesium), a composite oxide having a garnet-type crystal structure and containing a rare earth element and Al (aluminum), and a composite oxynitride containing Mg and Al, in which the oxide and composite oxynitride particles are scattered among the aluminum nitride crystal particles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 221504 Summary of the Invention [Problem to be solved by the invention]

[0005] Considering technological trends related to semiconductor integrated circuits, it is expected that the need for ceramic components with excellent insulating properties in high temperature ranges will continue to increase in the future. The technique disclosed in this specification aims to provide an aluminum nitride sintered body and an electrostatic chuck that have excellent insulating properties in high temperature regions. [Means for solving the problem]

[0006] The aluminum nitride sintered body according to the present disclosure contains aluminum nitride as a main component, a composite oxide containing a rare earth element and aluminum, and magnesium oxide, wherein the composite oxide and the magnesium oxide are present between particles of the aluminum nitride, and the volume resistivity at 600°C is 1.0 × 10 9 Ωcm or more 1.0×10 12 It is less than Ωcm. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide an aluminum nitride sintered body and an electrostatic chuck that have excellent insulating properties in high temperature regions. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing an example of an electrostatic chuck. [Figure 2] FIG. 2 is a table showing the profiles of the aluminum nitride sintered bodies according to the examples and comparative examples, and the volume resistivity measured for each aluminum nitride sintered body. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. <1> The aluminum nitride sintered body according to the present disclosure contains aluminum nitride as a main component, a composite oxide containing a rare earth element and aluminum, and magnesium oxide, wherein the composite oxide and the magnesium oxide are present between particles of the aluminum nitride, and the volume resistivity at 600°C is 1.0 × 10 9 Ωcm or more 1.0×10 12 It is less than Ωcm.

[0010] According to the above-mentioned configuration, since magnesium oxide having a higher volume resistivity than aluminum nitride is present between the aluminum nitride particles of the aluminum nitride sintered body, it is possible to obtain an aluminum nitride sintered body that can exhibit a predetermined volume resistivity even in a high temperature range. The aluminum nitride sintered body having the above-mentioned configuration is particularly suitable for use in an electrostatic chuck that utilizes the Johnsen-Rahbek force.

[0011] <2> the above <1> In the aluminum nitride sintered body, when the weight of the aluminum nitride is taken as 100, the weight a of the composite oxide and the weight b of the magnesium oxide preferably satisfy the following formulas (1) and (2). 0 <a≦10 …(1) 0 <b≦10 …(2)

[0012] Aluminum nitride raw powder is oxidized in the atmosphere, and oxygen substitutes for nitrogen atoms to form a solid solution. It is known that this process results in defects (vacancies) in the aluminum nitride, resulting in a decrease in insulating properties. In the manufacturing process of sintered aluminum nitride, rare earth oxide powder containing a rare earth element is added to aluminum nitride powder and sintered. The aluminum oxide contained in the aluminum nitride reacts with the rare earth oxide to form a composite oxide containing a rare earth element and aluminum, removing the dissolved oxygen in the aluminum nitride. This suppresses a decrease in volume resistivity. However, because the composite oxide has a lower volume resistivity than aluminum nitride, excessive generation of this composite oxide can result in an unnecessary decrease in volume resistivity. On the other hand, adding magnesium oxide powder to aluminum nitride powder and sintering the resulting powder to form a solid solution of magnesium in the aluminum nitride fills the defects in the aluminum nitride, suppressing a decrease in volume resistivity. Furthermore, the presence of magnesium oxide, which has high volume resistivity, between aluminum nitride particles can produce a high volume resistivity. However, the presence of a large amount of magnesium oxide in aluminum nitride inhibits sintering.

[0013] By setting the weight of the composite oxide relative to the aluminum nitride within the above range, the composite oxide can sufficiently remove dissolved oxygen in the aluminum nitride while suppressing excessive generation of the composite oxide and preventing a decrease in volume resistivity. Furthermore, by setting the weight of the magnesium oxide relative to the aluminum nitride within the above range, defects in the aluminum nitride can be filled and magnesium oxide with high volume resistivity can be present between the aluminum nitride particles without impairing sinterability. As a result, an aluminum nitride sintered body can be obtained that can exhibit a predetermined volume resistivity in the high temperature range while ensuring good sinterability.

[0014] <3> the above <2> In the aluminum nitride sintered body, it is preferable that the weight a and the weight b satisfy the following formula (3). 0< b / a ≦12 …(3)

[0015] If the ratio of the composite oxide to magnesium oxide is within the above range, these can be present in the aluminum nitride in a good balance, and an aluminum nitride sintered body capable of exhibiting a predetermined volume resistivity in a high temperature range can be obtained.

[0016] <4> the above <1> from <3> In the aluminum nitride sintered body, the average particle size of the aluminum nitride is preferably 1.0 μm or more and 10.0 μm or less. If the average particle size of the aluminum nitride particles is 10.0 μm or less, many grain boundaries of the aluminum nitride particles are contained in the aluminum nitride sintered body, and the composite oxide and magnesium oxide can be well dispersed in the aluminum nitride. Furthermore, if the average particle size is 1.0 μm or more, the overall volume resistivity can be maintained. According to the above configuration, an aluminum nitride sintered body that is highly uniform and can exhibit a predetermined volume resistivity can be obtained.

[0017] <5> The electrostatic chuck according to the present disclosure is <1> from <4> According to this configuration, an electrostatic chuck having excellent insulating properties in high temperature regions and suitable for semiconductor manufacturing at high temperatures can be obtained.

[0018] [Details of the embodiment] The aluminum nitride sintered body and electrostatic chuck according to the present disclosure will be specifically described below with reference to the drawings. The present disclosure is not limited to the following examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0019] (sintered aluminum nitride) The aluminum nitride sintered body according to this embodiment contains aluminum nitride (AlN) as a main component, a composite oxide containing a rare earth element and aluminum, and magnesium oxide (MgO). Hereinafter, the composite oxide containing a rare earth element and aluminum may be referred to as an R-Al composite oxide. In the aluminum nitride sintered body according to this embodiment, R-Al composite oxide and magnesium oxide are present between the aluminum nitride particles, and the volume resistivity at 600°C is 1.0 × 10 9 Ωcm or more 1.0×10 12 It is less than Ωcm.

[0020] (aluminum nitride) The aluminum nitride sintered body according to this embodiment is mainly composed of aluminum nitride (AlN) and contains 70% by weight or more, preferably 80% by weight or more, and more preferably 90% by weight or more of aluminum nitride. Aluminum nitride sintered bodies are known to have excellent mechanical strength and thermal shock resistance, high volume resistivity and thermal conductivity, and to exhibit high corrosion resistance, particularly against halogen-based gases and halogen-based plasmas.

[0021] In the aluminum nitride sintered body according to this embodiment, the aluminum nitride preferably forms crystal grains having an average grain size of 10.0 μm or less, more preferably 8.0 μm or less, and even more preferably 6.0 μm or less. If the average grain size of the aluminum nitride particles is equal to or less than the above range, many grain boundaries of the aluminum nitride crystal grains will be contained in the aluminum nitride sintered body, and the R-Al composite oxide and magnesium oxide can be well dispersed among the aluminum nitride crystal grains. Furthermore, the aluminum nitride preferably forms crystal grains having an average grain size of 1.0 μm or more. If the average grain size is equal to or greater than the above range, the overall volume resistivity can be maintained. When the aluminum nitride crystal grains have an average grain size that satisfies both of the above ranges, an aluminum nitride sintered body that is highly uniform and can exhibit a predetermined volume resistivity can be obtained.

[0022] (R-Al composite oxide) The aluminum nitride sintered body according to this embodiment contains a composite oxide (R-Al composite oxide) containing a rare earth element (R) and aluminum (Al). In the aluminum nitride sintered body according to the present disclosure, the R-Al composite oxide is present between aluminum nitride particles.

[0023] It is known that aluminum nitride raw powder oxidizes in the atmosphere, and oxygen displaces nitrogen atoms into solid solution, creating defects (vacancies) in the aluminum nitride and reducing its insulating properties. In the manufacturing process for sintered aluminum nitride, rare earth oxide powder containing rare earth elements is added to aluminum nitride powder and sintered. When the aluminum oxide contained in the aluminum nitride reacts with the rare earth oxide, an R-Al composite oxide containing rare earth elements and aluminum is produced. This removes the dissolved oxygen in the aluminum nitride, suppressing a decrease in volume resistivity.

[0024] Examples of the rare earth element (R) contained in the R-Al composite oxide include yttrium (Y), lanthanum (La), cerium (Ce), holmium (Ho), gadolinium (Gd), neodymium (Nd), samarium (Sm), dysprosium (Dy), ytterbium (Yb), erbium (Er), and lutetium (Lu). Of these, yttrium is particularly preferred.

[0025] In R-Al composite oxides, rare earth elements and aluminum are combined in a specific ratio to form a garnet-type oxide (R3Al5O 12 ), perovskite type (RAlO3), monoclinic type (R4Al2O9), etc. are formed. Among them, R-Al composite oxides having a garnet type crystal structure with high volume resistivity are preferred. When yttrium is used as the rare earth element, the R-Al composite oxide is Y3Al5O 12 Crystal structures such as (YAG), YAlO3 (YAP), and Y4Al2O9 (YAM) are formed.

[0026] The content of the R-Al composite oxide contained in the aluminum nitride sintered body according to this embodiment is preferably greater than 0 parts by weight, and more preferably greater than 0.5 parts by weight, per 100 parts by weight of aluminum nitride. If the content of the R-Al composite oxide is equal to or greater than the above range, the effect of removing dissolved oxygen can be obtained. On the other hand, since the volume resistivity of the R-Al composite oxide is lower than that of aluminum nitride, excessive generation of the R-Al composite oxide can result in an unnecessary decrease in volume resistivity. Therefore, the content of the R-Al composite oxide is preferably 10 parts by weight or less, and more preferably 9.5 parts by weight or less, per 100 parts by weight of aluminum nitride. If the content of the R-Al composite oxide is equal to or less than the above range, unnecessary decrease in volume resistivity due to excess R-Al composite oxide can be suppressed.

[0027] From the above, in the aluminum nitride sintered body according to this embodiment, when the weight of aluminum nitride is taken as 100, the weight a of the R-Al composite oxide preferably satisfies the following formula (1). 0 <a≦10 …(1)

[0028] (Magnesium oxide) The aluminum nitride sintered body according to this embodiment contains magnesium oxide (MgO), which is present between the aluminum nitride particles.

[0029] High volume resistivity can be achieved by allowing magnesium oxide, which has high volume resistivity, to exist between aluminum nitride particles. One possible solution to the problem of defects (voids) in aluminum nitride is to add magnesium oxide powder to aluminum nitride powder and sinter it to produce an aluminum nitride sintered body. In this case, magnesium dissolves in the aluminum nitride, filling in the defects in the aluminum nitride, and the resulting aluminum nitride sintered body contains magnesium within the aluminum nitride particles.

[0030] The content of magnesium oxide contained in the aluminum nitride sintered body according to this embodiment is preferably more than 0 parts by weight, and more preferably 1.0 part by weight or more, per 100 parts by weight of aluminum nitride. If the magnesium oxide content is above this level, defects are filled and magnesium oxide can be present between the aluminum nitride particles. On the other hand, if magnesium oxide is present in excess, sintering is inhibited. Therefore, the magnesium oxide content is preferably 10 parts by weight or less per 100 parts by weight of aluminum nitride. If the magnesium oxide content is below this level, defects during sintering due to the presence of excess magnesium oxide can be suppressed.

[0031] From the above, in the aluminum nitride sintered body according to this embodiment, when the weight of aluminum nitride is taken as 100, the weight b of magnesium oxide preferably satisfies the following formula (2). 0 <b≦10 …(2)

[0032] In the aluminum nitride sintered body according to this embodiment, when the weight of aluminum nitride is taken as 100, the weight a of the R-Al composite oxide and the weight b of magnesium oxide preferably satisfy the following formula (3). 0< b / a ≦12 …(3)

[0033] When the ratio of R-Al composite oxide to magnesium oxide is within the above range, these can be present in the aluminum nitride in a good balance, and an aluminum nitride sintered body capable of exhibiting a predetermined volume resistivity in a high temperature range can be obtained. Within the above range, b / a is preferably 1 or more, and more preferably 5 or more.

[0034] (Method of manufacturing aluminum nitride sintered body) The aluminum nitride sintered body according to this embodiment can be produced, for example, by preparing a mixture containing aluminum nitride powder, a rare earth element oxide, and magnesium oxide powder, press-molding the resulting mixture, and sintering the resulting molded body.

[0035] In the above-mentioned production method, the mixture can be prepared by any known method, whether wet or dry, using a rotary ball mill, a vibration ball mill, a bead mill, high-speed stirring, etc. When wet mixing is carried out with the addition of a solvent, the mixture can be dried after mixing to obtain a raw material mixed powder.

[0036] In the above-mentioned manufacturing method, press molding can be performed by a known molding method such as a mold molding method, a cold isostatic pressing (CIP) method, a slip casting method, or an extrusion molding method. These methods may also be combined. For example, a molded body can be obtained by performing uniaxial pressing using a mold press and then performing an isostatic treatment. In this way, a more homogeneous and dense molded body can be obtained.

[0037] In the above manufacturing method, the sintering is not particularly limited, but is preferably carried out in an inert gas atmosphere at a temperature of 1000°C to 2000°C. Sintering may be carried out at normal pressure, but is preferably carried out under pressure by hot pressing. In this way, a more homogeneous and dense sintered body can be obtained.

[0038] (volume resistivity) The aluminum nitride sintered body according to this embodiment has a melting point of 1.0×10 at 600°C. 9 Ωcm or more 1.0×10 12 It has a volume resistivity of Ωcm or less. Here, the volume resistivity refers to the value measured in a nitrogen atmosphere by the DC three-terminal method in accordance with JIS C2141. Usually, the volume resistivity of aluminum nitride sintered bodies is 1.0 × 10 at room temperature (20°C). 14 Although the resistance is high at Ωcm or more, at high temperatures above 600°C it is 1.0×10 8 However, in the aluminum nitride sintered body according to this embodiment, as described above, the R-Al composite oxide and magnesium oxide are present between the aluminum nitride crystal grains, which prevents the volume resistivity from decreasing at high temperatures and maintains a high volume resistivity even at 600°C.

[0039] (electrostatic chuck) The aluminum nitride sintered body of this embodiment can be particularly suitably used for electrostatic chucks, which require high volume resistivity in high-temperature, high-voltage environments. 1 shows an example of an electrostatic chuck 1 manufactured using the aluminum nitride sintered body of this embodiment. The electrostatic chuck 1 holds a wafer W, which is an object to be processed, in, for example, a semiconductor manufacturing device.

[0040] As shown in FIG. 1 , the electrostatic chuck 1 includes a ceramic plate 10 made of the aluminum nitride sintered body of this embodiment and an electrode 20 made of a conductor such as a metal embedded inside the ceramic plate 10. The electrode 20 is what is called an electrostatic electrode. When a voltage is applied to the electrode 20, charges generated in the ceramic plate 10 move to the outermost surface of the ceramic plate 10, and charges of the opposite polarity are generated on the backside of the wafer W placed opposite the surface of the ceramic plate 10. A small current flows through the interface gap between the dielectric ceramic plate 10 and the wafer W, which is the object, causing charge polarization, resulting in the wafer W being strongly attracted and held on the surface of the ceramic plate 10. The force that attracts the wafer W onto the ceramic plate 10 in this way is called the Johnsen-Rahbek force. In order for the Johnsen-Rahbek force to be generated, a force of 1.0×10 must be applied under the operating environment. 9 Ωcm or more 1.0×10 12 It has been found that it is preferable to use a ceramic plate 10 having a volume resistivity of Ωcm or less.

[0041] In recent years, due to the miniaturization and high density of semiconductor integrated circuits, wafers W are processed at high temperatures of 600° C. or higher. The ceramic plate 10 of the electrostatic chuck 1 according to this embodiment has a thermal conductivity of 1.0×10 at 600° C. 9 Ωcm or more 1.0×10 12 The electrostatic chuck 1 according to this embodiment is made of an aluminum nitride sintered body having a volume resistivity of Ωcm or less. Therefore, the electrostatic chuck 1 according to this embodiment is very suitable for use in semiconductor manufacturing equipment that processes wafers W at high temperatures of 600° C. or higher.

[0042] (Effects of the embodiment) As described above, the aluminum nitride sintered body according to this embodiment contains aluminum nitride (AlN) as a main component, a composite oxide containing a rare earth element and aluminum (R-Al composite oxide), and magnesium oxide (MgO), and the R-Al composite oxide and the magnesium oxide are present between the aluminum nitride particles, and the volume resistivity at 600°C is 1.0 × 10 9 Ωcm or more 1.0×1012 It is less than Ωcm.

[0043] According to the above-mentioned configuration, since magnesium oxide having a higher volume resistivity than aluminum nitride is present between the aluminum nitride particles of the aluminum nitride sintered body, it is possible to obtain an aluminum nitride sintered body that can exhibit a predetermined volume resistivity in a high temperature range. The aluminum nitride sintered body having the above-mentioned configuration is particularly suitable for use in an electrostatic chuck that utilizes the Johnsen-Rahbek force.

[0044] Furthermore, in the aluminum nitride sintered body according to this embodiment, when the weight of the aluminum nitride is taken as 100, the weight a of the composite oxide (R-Al composite oxide) and the weight b of the magnesium oxide satisfy the following formulas (1) and (2): 0 <a≦10 …(1) 0 <b≦10 …(2)

[0045] By setting the weight of the R-Al composite oxide relative to the aluminum nitride within the above range, it is possible to sufficiently remove dissolved oxygen from the aluminum nitride while suppressing the formation of excess R-Al composite oxide. Furthermore, by setting the weight of the magnesium oxide relative to the aluminum nitride within the above range, it is possible to allow magnesium oxide to exist between the aluminum nitride particles to an extent that does not impair sinterability. As a result, it is possible to obtain an aluminum nitride sintered body that can exhibit a predetermined volume resistivity at high temperatures while ensuring good sinterability.

[0046] Moreover, in the aluminum nitride sintered body according to this embodiment, the weight a and the weight b further satisfy the following formula (3). 0< b / a ≦12 …(3)

[0047] When the ratio of R-Al composite oxide to magnesium oxide is within the above range, they are present in the aluminum nitride in a good balance, and an aluminum nitride sintered body capable of exhibiting a predetermined volume resistivity in the high temperature range can be obtained. In particular, by setting the ratio b / a to 5≦b / a ≦12, it is possible to obtain an aluminum nitride sintered body capable of exhibiting a predetermined volume resistivity in the high temperature range. 10It is possible to obtain an aluminum nitride sintered body that can exhibit an excellent volume resistivity of Ωcm or more.

[0048] Furthermore, in the aluminum nitride sintered body according to this embodiment, the average particle size of the aluminum nitride is 1.0 μm or more and 10.0 μm or less. If the average particle size of the aluminum nitride particles is 10.0 μm or less, many grain boundaries of the aluminum nitride particles are contained in the aluminum nitride sintered body, and the R-Al composite oxide and magnesium oxide can be well dispersed in the aluminum nitride. Furthermore, if the average particle size is 1.0 μm or more, the overall volume resistivity can be maintained. If the average particle size of the aluminum nitride particles is within the above range, an aluminum nitride sintered body that is highly uniform and can exhibit a predetermined volume resistivity can be obtained.

[0049] The electrostatic chuck according to the present embodiment includes the aluminum nitride sintered body according to the present embodiment. With this configuration, an electrostatic chuck having excellent insulating properties in high-temperature regions and suitable for semiconductor manufacturing at high temperatures can be obtained.

[0050] <Other embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included within the technical scope of the present invention.

[0051] (1) The electrostatic chuck is not limited to that described in the above embodiment. In addition to the electrode 20, which is an electrostatic electrode, one or more electrodes for maintaining the wafer at a predetermined temperature may be further provided. A flow path for circulating gas or liquid may be provided inside the ceramic plate. The shape of the electrostatic chuck is not limited to a disk shape and may be various shapes. [Example]

[0052] The present technology will be described in more detail below based on examples, but the present technology is not limited to these examples.

[0053] (sintered aluminum nitride) [Examples 1 to 11, Comparative Examples 1 to 3] Aluminum nitride powder, yttrium oxide powder, and magnesium oxide powder were weighed out so that the amounts of R-Al composite oxide and magnesium oxide in the aluminum nitride sintered body were as shown in the table in Figure 2. The weighed raw material powders were added to ethanol as a solvent, mixed in a ball mill, and dried to prepare a mixed powder. The resulting mixed powder was uniaxially pressed using a mold press at a pressure of 12 MPa, and then subjected to isostatic pressure treatment at 147 MPa to produce a disk-shaped compact approximately 60 mm in diameter and 9 mm thick. The compact was packed into a carbon die and sintered by hot pressing in a nitrogen atmosphere at a sintering temperature of 1830°C, a holding time of 2 hours, and a pressure of 4.4 MPa to produce an aluminum nitride sintered body.

[0054] (Analysis and Evaluation) [Weight ratio] The powders obtained by pulverizing the aluminum sintered bodies according to the above examples and comparative examples were measured using a synchrotron X-ray diffractometer, and the diffraction patterns were quantitatively analyzed using the WPPF (Whole Powder Pattern Fitting) method to calculate the weight ratios. The results are shown in the table in Figure 2.

[0055] [Average particle size] The average particle size of aluminum nitride contained in the aluminum sintered bodies according to the above examples and comparative examples was measured by the intercept method after observing the fracture surfaces of the sintered bodies with an SEM. The results are shown in the table of FIG.

[0056] [Volume resistivity] Test pieces were cut out from the aluminum sintered bodies according to the above examples and comparative examples in accordance with JIS C2141, and their volume resistivities were measured at 600°C in a nitrogen atmosphere by the DC three-terminal method in accordance with JIS C2141. The results are shown in the table of FIG.

[0057] As shown in the table of FIG. 2, the aluminum nitride sintered bodies of Examples 1 to 11 all had a melting point of 1.1 × 10 at 600°C. 9 A high volume resistivity of Ωcm or more was maintained. The crystalline phase contains R-Al composite oxides, Y3Al5O 12 The aluminum nitride sintered bodies of Examples 1, 2, 3, 7, and 11, which include 9 Furthermore, when the weight ratio of the R-Al composite oxide (a) and magnesium oxide (b) to 100 parts by weight of aluminum nitride is taken into account, the aluminum nitride sintered bodies of Examples 1, 2, 3, 4, 7, and 11, in which b / a was 1 or more, exhibited a volume resistivity of 7.0 × 10 at 600°C. 9 Among them, the aluminum nitride sintered body of Example 1, in which b / a was 5 or more, exhibited a high volume resistivity of 1.0 × 10 10 The aluminum nitride sintered body of Example 11 has a resistivity of 2.0 × 10 at 600 °C and a b / a ratio of 10 or more. 10 It exhibited an excellent volume resistivity of Ωcm or more.

[0058] In contrast, the aluminum nitride sintered bodies of Comparative Examples 1 to 3 all had a volume resistivity of 1.8 × 10 at 600 °C. 8 The resistivity was Ωcm or less. The aluminum nitride sintered body of Comparative Example 1 did not contain magnesium oxide, the aluminum nitride sintered body of Comparative Example 2 had a magnesium oxide content (b) greater than 10 parts by weight relative to 100 parts by weight of aluminum nitride, and the aluminum nitride sintered body of Comparative Example 3 had an R-Al composite oxide content (a) greater than 10 parts by weight. In Comparative Example 1, the volume resistivity was thought to have decreased due to defects (voids) formed in the aluminum nitride. In Comparative Example 2, the amount of magnesium oxide was excessive, which presumably prevented the aluminum nitride sintered body from being sintered well, resulting in a lower volume resistivity than in the Examples. In Comparative Example 3, the volume resistivity was thought to have decreased compared to the Examples because the aluminum nitride contained an excess amount of R-Al composite oxide, which has a lower volume resistivity than aluminum nitride. [Explanation of symbols]

[0059] 1: Electrostatic chuck 10: Ceramic plate 20: Electrode W: Wafer

Claims

1. The main component is aluminum nitride, a composite oxide containing a rare earth element and aluminum; magnesium oxide, the composite oxide and the magnesium oxide are present between the aluminum nitride particles, The volume resistivity at 600°C is 1.0 × 10 ９ Ωcm or more and 2.3×10 Ωcm or less, An aluminum nitride sintered body, wherein when the weight of the aluminum nitride is taken as 100, the weight b of the magnesium oxide satisfies the following formula (2): 5≦b≦10 ... (2)

2. 2. The aluminum nitride sintered body according to claim 1, wherein when the weight of the aluminum nitride is taken as 100, the weight a of the composite oxide satisfies the following formula (1): 0 < a ≦ 10 ... (1)

3. 3. The aluminum nitride sintered body according to claim 2, wherein the weight a and the weight b satisfy the following formula (3): 0<b / a≦12…(3)

4. 4. The aluminum nitride sintered body according to claim 1, wherein the aluminum nitride has an average particle size of 1.0 μm or more and 10.0 μm or less.

5. An electrostatic chuck comprising the aluminum nitride sintered body according to claim 1 .

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